Alcohols have been extensively utilized in antimicrobial formulations to provide a reduction in populations of viable microorganisms. Methanol, ethanol, and N-butanol can each be produced by fermentation and alcohols such as 2-propanol, 2-butanol, 2-pentanol, and so on, can be synthesized from petrochemicals.
Because 2-propanol (also referred to as isopropanol) has proven more effective than ethanol and methanol in reducing populations of viable microorganisms its use has become widespread in conventional antimicrobial formulations. The superior efficacy of isopropanol over methanol and ethanol can be understood, in part, by considering the physical properties as summarized in TABLE 1.
TABLE 1Azeotrope with WaterChemicalLog P% w/w% v/vFPMethanol−0.70NANA11° C.Ethanol−0.3095%94%22° C.Acetone−0.23NANA−18° C. Isopropanol0.0587%83%21° C.
The effect of the alcohol as an antimicrobial material may in part be related to concentration and in part duration of time in contact with the target microbe. Additionally, the effectiveness of an alcohol or other antimicrobial material in reducing populations of microorganisms may also be due to its log P, also referred to as the Log Pow. Log Pow is the log10 of the ratio of the equilibrium concentrations of the alcohol or other antimicrobial material in 1-octanol saturated with water (COi) and water saturated with 1-octanol (CWi). Log Pow=log10(COi/CWi). Negative values of Log Pow represent substances that are more soluble in water, while positive values of Log Pow represent substances that are more soluble in n-octanol. In general, the more soluble an antimicrobial material is in n-octanol the more effective the antimicrobial material may be in reducing populations of microorganisms in aqueous solutions. It may be predicted that isopropanol will be a more effective antimicrobial than methanol, ethanol, and acetone based on the Log Pow.
While alcohols such as methanol, ethanol, and isopropanol and ketones such as acetone have proven effective in reducing viable populations of microorganisms, certain substantial problems remain unaddressed with their use.
A first substantial problem with the use of certain alcohols such as methanol and certain ketones such as acetone in or as compositions for the reduction of viable populations of microorganisms can be their relatively high vapor pressures and relatively low flashpoints (FP). In this regard, alcohols and ketones conventionally included in antimicrobial compositions can have vapor pressures and flashpoints which allow ignition even without direct contact with the ignition source and may be regulated as workplace hazards. Additionally, alcohols and ketones conventionally used as or in antimicrobial compositions may have to be shipped as flammable materials under United States Department of Transportation (“DOT”) guidelines. Flammable materials can be more costly to transport than materials which are not characterized as flammable under DOT guidelines.
Another substantial problem with the use of alcohols such as methanol, ethanol and isopropanol and ketones such as acetone can be that upon application to viable populations of microorganisms the rate of evaporation can limit the duration of time a viable population of microorganisms is exposed to alcohol or ketone. Even as aqueous mixtures, alcohols and ketones can evaporate from the aqueous mixture at a rate which alters the efficacy of the mixture as the concentration of the alcohol or ketone in the mixture reduces over time.
The instant invention provides a differential evaporation potentiated disinfectant system which provides antimicrobial compositions and methods of using such antimicrobial compositions to potentiate the active components of the composition for the reduction of viable populations of microorganisms in conditioning, cleaning or disinfection of surfaces.